Display device

ABSTRACT

A display device includes a first substrate including a display region and a non-display region, the non-display region being positioned on an outside of the display region, a first dam in the non-display region of the substrate, the first dam including a first barrier and a first stopper, the first stopper being on the first barrier and having a concave groove formed thereon, and a first alignment layer covering the display region of the first substrate, at least a part of the first alignment layer extending to the non-display region and contacting a surface of the first stopper.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application based on pending U.S. patentapplication Ser. No. 16/184,075, filed Nov. 8, 2018, the disclosure ofwhich is incorporated herein by reference in its entirety. U.S. patentapplication Ser. No. 16/184,075 is a continuation application of U.S.patent application Ser. No. 15/826,219, filed Nov. 29, 2017, now U.S.Pat. No. 10,134,774, issued Nov. 20, 2018, the disclosure of which isincorporated herein by reference in its entirety. U.S. patentapplication Ser. No. 15/826,219 is a continuation application of U.S.patent application Ser. No. 15/177,364, filed Jun. 9, 2016, now U.S.Pat. No. 9,837,445, issued Dec. 5, 2017, the disclosure of which isincorporated herein by reference in its entirety. U.S. Pat. No.9,837,445 claims priority benefit of Korean Patent Application No.10-2015-0144555, filed on Oct. 16, 2015, in the Korean IntellectualProperty Office, entitled, “Display Device and Method for Fabricatingthe Same,” the disclosure of which is incorporated herein by referencein its entirety for all purposes.

BACKGROUND 1. Field

Embodiments relate to a display device and a method for fabricating thesame.

2. Description of the Related Art

A liquid crystal display, which is a type of display device that hasbeen widely used, can adjust the quantity of penetrating light byapplying a voltage to electrodes (a pixel electrode and a commonelectrode) formed on two opposite substrates and controlling anarrangement of liquid crystal molecules of a liquid crystal layerinterposed between the two substrates.

SUMMARY

Embodiments are directed to a display device including a first substrateincluding a display region and a non-display region, the non-displayregion being positioned on an outside of the display region, a first damin the non-display region of the substrate, the first dam including afirst barrier and a first stopper, the first stopper being on the firstbarrier and having a concave groove formed thereon, and a firstalignment layer covering the display region of the first substrate, atleast a part of the first alignment layer extending to the non-displayregion and contacting a surface of the first stopper.

Each of the first barrier and the first stopper may extend to form aclosed curve surrounding the display region of the first substrate.

The first barrier may form a continuous straight line along eachextension direction surrounding the display region of the firstsubstrate. The first stopper may form an uneven line along eachextension direction surrounding the display region of the firstsubstrate.

The first stopper may have a width that is smaller than a width of thefirst barrier in a direction that is perpendicular to an extensiondirection.

The first stopper may be on at least a part of a side surface of thefirst barrier and an upper surface of the first barrier.

The first stopper may have a continuous shape or a separated shape on atleast the part of the side surface of the first barrier and the uppersurface of the first barrier.

A minimum thickness of the first stopper may be equal to or greater thana thickness of a portion of the first alignment layer that is in thedisplay region of the first substrate, and a portion of the firstalignment layer that contacts a surface of the first stopper may have athickness that is greater than a thickness of a portion of the firstalignment layer that is in the display region of the first substrate.

A color filter may be in the display region of the first substrate. Thefirst barrier may include the same material as the color filter.

The display device may further include a second substrate opposite tothe first substrate in a state where the first alignment layer isinterposed between the second substrate and the first substrate, thesecond substrate including a display region and a non-display regioncorresponding to the display region and the non-display region of thefirst substrate, a second dam including a second barrier and a secondstopper on the second barrier and having a concave groove formed on asurface thereof, the second dam being in the non-display region of thesecond substrate, and a second alignment layer covering the displayregion of the second substrate, at least a part of the second alignmentlayer extending to the non-display region and contacting a surface ofthe second stopper.

Each of the second barrier and the second stopper may extend to form aclosed curve that surrounds the display region of the second substrate.

The second barrier may form a continuous straight line along anextension direction. The second stopper may form an uneven line alongthe extension direction.

A minimum thickness of the second stopper may be equal to or greaterthan a thickness of a portion of the second alignment layer that is inthe display region of the second substrate. A portion of the secondalignment layer contacts a surface of the second stopper has a thicknessthat is greater than a thickness of a portion of the second alignmentlayer that is in the display region of the second substrate.

A column spacer may be arranged in the display region of the secondsubstrate. The second barrier may include the same material as thecolumn spacer.

Each of the first stopper and the first alignment layer may include analignment material. The alignment material of the first stopper may bedifferent from the alignment material of the first alignment layer.

Embodiments are also directed to a method for fabricating a displaydevice including preparing a first substrate including a display regionand a non-display region located on an outside of the display region,forming a first dam in the non-display region of the first substratesuch that first dam includes a first barrier and a first stopper on thefirst barrier, the first stopper having a concave groove formed thereon,and forming a first alignment layer covering the display region of thefirst substrate, at least a part of the first alignment layer extendingup to the non-display region and contacting a surface of the firststopper.

Forming the first barrier may include forming the first barrier togetherwith forming a color filter in the display region of the first substratethrough a patterning process. Forming the first stopper may includeapplying an alignment solution that includes an alignment material onthe first barrier using a dispensing process.

Forming the first alignment layer may include discharging an alignmentsolution onto the display region of the first substrate using a printingprocess. The alignment solution that forms the first alignment layer mayinclude an alignment material that is different from the alignmentmaterial that forms the first stopper.

The viscosity of the alignment solution of the first stopper may behigher than the viscosity of the alignment solution of the firstalignment layer.

The method may further include preparing a second substrate including adisplay region and a non-display region corresponding to the displayregion and the non-display region of the first substrate, respectively,forming a second dam arranged in the non-display region of the secondsubstrate, the second dam including a second barrier and a secondstopper arranged on the second barrier, the second stopper having aconcave groove on a surface thereof, forming a second alignment layercovering the display region of the second substrate, at least a part ofthe second alignment layer extending up to the non-display region andcontacting a surface of the second stopper, and interposing a sealingmember between the first substrate and the second substrate.

Forming the second barrier may include forming the second barriertogether with forming a column spacer in the display region of thesecond substrate through a patterning process. Forming the secondstopper may include applying an alignment solution that includes analignment material on the second barrier using a dispensing process.

BRIEF DESCRIPTION OF THE DRAWINGS

Features will become apparent to those of skill in the art by describingin detail exemplary embodiments with reference to the attached drawingsin which:

FIG. 1 illustrates a schematic view depicting a display device accordingto an embodiment;

FIG. 2 illustrates a cross-sectional view taken along line I-I′ of FIG.1;

FIG. 3 illustrates an enlarged cross-sectional view of portion “A” ofFIG. 2;

FIG. 4 illustrates a top view showing an arrangement relationshipbetween a first dam and a first alignment layer of FIG. 2;

FIGS. 5 to 7 illustrate cross-sectional views showing variousembodiments of a first dam and a second dam; and

FIGS. 8 to 18 illustrate cross-sectional views explaining stages of amethod for fabricating a display device of FIG. 1.

DETAILED DESCRIPTION

Example embodiments will now be described more fully hereinafter withreference to the accompanying drawings; however, they may be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey exemplary implementations to those skilled in the art.

In the drawing figures, the dimensions of layers and regions may beexaggerated for clarity of illustration. It will also be understood thatwhen a layer or element is referred to as being “on” another layer orsubstrate, it can be directly on the other layer or substrate, orintervening layers may also be present. Like reference numerals refer tolike elements throughout.

FIG. 1 illustrates a schematic view depicting a display device accordingto an embodiment.

Referring to FIG. 1, a display device 10 according to an embodiment mayinclude a first display panel 100, a second display panel 200 oppositeto the first display panel 100, and a sealing member 300 bonding thefirst display panel 100 and the second display panel 200 to each other.A liquid crystal layer LCL (in FIG. 2) may be interposed between thefirst display panel 100 and the second display panel 200.

The first display panel 100 may include a display region DA thatdisplays an image thereon, the display region DA may including aplurality of pixels that are arranged in the form of a matrix in a firstdirection X and a second direction Y that crosses the first direction X,and a non-display region NDA that is positioned on an outside of thedisplay region DA to surround the display region DA. In the displayregion DA of the first display panel 100, a plurality of firstelectrodes (also called pixel electrodes) PE (in FIG. 2), wirings thatdrive the first electrodes, and a plurality of thin film transistors TR(in FIG. 1) may be arranged. In the non-display region NDA of the firstdisplay panel 100, a drive portion that applies driving signals to thedisplay region DA through the wirings may be arranged.

The second display panel 200 may be oppositely coupled to the firstdisplay panel 100. The second display panel 200 may include a displayregion and a non-display region that respectively correspond to thedisplay region DA and the non-display region NDA of the first displaypanel 100. Accordingly, hereinafter, the display region and thenon-display region of the second display panel 200 are respectivelycalled “DA” and “NDA”.

The sealing member 300 may be interposed between the first display panel100 and the second display panel 200 to surround the display region DAin the non-display regions NDA of the first display panel 100 and thesecond display panel 200, and to couple a first substrate 110 and asecond substrate 210 to each other.

In the non-display regions NDA of the first display panel 100 and thesecond display panel 200, a first dam 160 and a second dam 250 may bearranged in a region adjacent to the display region DA to surround thedisplay region DA. The first dam 160 and the second dam 250 will bedescribed in detail below.

Hereinafter, the detailed configuration of the display device 10 will bedescribed.

FIG. 2 is a cross-sectional view taken along line I-I′ of FIG. 1.

Referring to FIG. 2, the first display panel 100 of the display device10 may include a first substrate 110, a thin film transistor TR, a firstinsulating layer 120, a second insulating layer 130, a color filter 140,a third insulating layer 150, a first electrode (or pixel electrode) PE,a first dam 160, and a first alignment layer 170, which are stacked in athird direction Z that is perpendicular to the first direction X.

The first substrate 110 may include the display region DA and thenon-display region NDA that are defined on the first display panel 100.The first substrate 110 may include an insulating material, such astransparent glass, quartz, ceramic, silicon, or transparent plastic. Theinsulating material may be appropriately selected in accordance with aneed of a manufacturer. In some embodiments, the first substrate 110 mayhave flexibility. For example, the first substrate 110 may be asubstrate having a shape that is changeable, for example, by rolling,folding, or bending.

The thin film transistor TR may be arranged in the display region DA ofthe first substrate 110. The thin film transistor TR may include a gateelectrode GE connected to a gate line, a semiconductor layer SM, asource electrode SE connected to a data line, and a drain electrode DE.

The gate electrode GE may be arranged in the display region DA of thefirst substrate 110 The gate electrode GE may be formed to project fromthe gate line that extends in the first direction X on a plane towardthe semiconductor layer SM. The gate electrode GE may include any one ofindium tin oxide (ITO), indium zinc oxide (IZO), and indium tin zincoxide (ITZO). In some implementations, the gate electrode GE may have atwo-layer structure that includes a first electrode layer that is madeof the above-described material and a second electrode layer that ismade of a a metal, such as copper (Cu), molybdenum (Mo), aluminum (Al),tungsten (W), chromium (Cr), or titanium (Ti), or an alloy including atleast one of the above-described metals.

The semiconductor layer SM may be arranged on the gate electrode GE in astate where the first insulating layer 120 is interposed between thesemiconductor layer SM and the gate electrode GE. The semiconductorlayer SM may include an activation layer that is provided on the firstinsulating layer 120 and an ohmic contact layer that is provided on theactivation layer. In some implementations, the semiconductor layer SMmay be arranged between the data line extending in the second directionY (in FIG. 1) and the first insulating layer 120.

The source electrode SE may be arranged on the semiconductor layer SM,and may overlap at least a part of the gate electrode GE on a plane. Thesource electrode SE may be formed to project from the data line. Thedrain electrode DE may be arranged on the semiconductor layer SM to bespaced apart from the source electrode SE, and may overlap at least apart of the gate electrode GE on a plane. The source electrode SE andthe drain electrode DE may be made of a metal, such as copper,molybdenum, aluminum, tungsten, chromium, or titanium, or an alloyincluding at least one of the above-described metals. The sourceelectrode SE and the drain electrode DE may overlap a part of thesemiconductor layer in a region excluding an apart region between thesource electrode SE and the drain electrode DE.

The first insulating layer 120 may be arranged in the display region DAand the non-display region NDA of the first substrate 110, and may beinterposed between the gate electrode GE and the semiconductor layer SMto electrically insulating the gate electrode GE and the semiconductorlayer SM from each other. The first insulating layer 120 may include aninsulating material, for example, silicon nitride or silicon oxide. Insome implementations, the data line may be arranged on the firstinsulating layer 120.

The second insulating layer 130 may be arranged in the display region DAand the non-display region NDA on the first insulating layer 120. Thesecond insulating layer 130 may cover the source electrode SE and thedrain electrode DE. The second insulating layer 130 may have athrough-hole that exposes the drain electrode DE. The second insulatinglayer 130 may include an insulating material, for example, siliconnitride or silicon oxide.

The color filter 140 may be arranged corresponding to each pixel of thedisplay region DA on the second insulating layer 130. The color filter140 may provide a color to light that penetrates the liquid crystallayer LCL. The color filter 140 may include one of a red filter, a greenfilter, and a blue filter, as examples. The color filter 140 may includean organic material. In some implementations, a first barrier 161 of thefirst dam 160 may be arranged on the second insulating layer 130 in thenon-display region NDA. The first barrier 161 of the first dam 160 willbe described in detail below.

The third insulating layer 150 may be arranged in the display region DAand the non-display region NDA on the second insulating layer 130. Thethird insulating layer 150 may cover the color filter 140 and the firstbarrier 161 of the first dam 160. In this case, the third insulatinglayer 150 may be conformably formed along the first barrier 161 of thefirst dam 160. The third insulating layer 150 may include an insulatingmaterial, for example, silicon nitride or silicon oxide. Like the secondinsulating layer 130, the third insulating layer 150 may include athrough-hole f that exposes the drain electrode DE.

The first electrode PE may be arranged corresponding to each pixel ofthe display region DA on the third insulating layer 150. The firstelectrode PE may be electrically connected to the drain electrode DE.The first electrode PE may include a transparent conductive material,for example, any one of indium tin oxide (ITO), indium zinc oxide (IZO),and indium tin zinc oxide (ITZO).

The first dam 160 may be arranged on a region of the non-display regionNDA that is adjacent to the display region DA on the first substrate110. The first dam 160 may include the first barrier 161 and a firststopper 162 that are stacked in the third direction Z.

The first barrier 161 may be arranged on the same layer as the colorfilter 140, for example, between the second insulating layer 130 and thethird insulating layer 150. The first barrier 161 may extend to surroundthe display region DA of the first substrate 110, and may form a closedcurve. The first barrier 161 may have a predetermined thickness T1 (inFIG. 3).

The first stopper 162 may be arranged on the third insulating layer 150to overlap the first barrier 161. Like the first barrier 161, the firststopper 162 may also extend to surround the display region DA of thefirst substrate 110 and may form a closed curve. The first stopper 162may have the lyophobic characteristic with respect to an alignmentsolution that is used when the first alignment layer 170 is formed, andmay have a thickness that is smaller than the thickness T1 (in FIG. 3)of the first barrier 161. For example, the maximum thickness T2 (in FIG.3) of the first stopper 162 may be smaller than the thickness T1 (inFIG. 3) of the first barrier 161.

The first stopper 162 may be formed using a dispensing process. Thefirst stopper 162 may include an alignment material having the lyophobiccharacteristic with respect to the alignment solution that is used whenthe first alignment layer 170 is formed. The alignment material of thefirst stopper 162 may be an organic polymer material. The organicpolymer material may include, for example, at least one of a polyimide,a polyamic acid, and a polysiloxane.

When forming the first alignment layer 170 that is arranged on the firstelectrode PE using a printing method such as an inkjet printing methodto apply an alignment solution including an alignment material, thefirst dam 160 may help to prevent the alignment solution that isdischarged onto the first electrode PE from spreading toward thenon-display region NDA. For example, the alignment solution dischargedonto the first electrode may have a tendency to spread due to spreadproperties of the alignment solution, and such spreading may be blockedby the first dam 160. For example, the first barrier 161 having thepredetermined thickness T1 may serve to primarily prevent theabove-described spreading. The first stopper 162 having the lyophobiccharacteristic with respect to the alignment solution may serve tosecondarily prevent the spreading. The details of the first dam 160 willbe described below.

The first alignment layer 170 may be arranged to cover the displayregion DA of the first substrate 110, for example, to cover the firstelectrode PE and the third insulating layer 150. At least a portion ofthe first alignment layer 170 may extend up to the non-display regionNDA of the first substrate 110 to come into contact with the surface ofthe first stopper 162 of the first dam 160. In this case, a part 170T ofthe first alignment layer 170 may overlap a part of a concave groove g1(in FIG. 3) of the first stopper 162. Such a structure may be obtainedin accordance with the limiting of flowing of the alignment solution tothe non-display region NDA by the first stopper 162, which has thelyophobic characteristic with respect to the alignment solution that isdischarged onto the first electrode PE and in accordance with increasinga resistive force against the flowing of the alignment solution to thenon-display region NDA using the groove g1 (in FIG. 3), in the casewhere the first alignment layer 170 is formed using a printing method,such as an inkjet printing method. In some implementations, in order toobtain good wettability of the alignment solution with respect to thefirst electrode PE and the third insulating layer 150 when the firstalignment layer 170 is formed, the surface of the first substrate 110,on which the third insulating layer 150 is formed, may have been treatedsuch that the whole surface of the first substrate 110 has the lyophiliccharacteristic.

The first alignment layer 170 as described above may serve to initiallyalign liquid crystal molecules LC of the liquid crystal layer LCL. Thefirst alignment layer 170 may include an alignment material. Thealignment material of the first alignment layer 170 may be an organicpolymer material. The organic polymer material may include, for example,at least one of a polyimide, a polyamic acid, and a polysiloxane.

The second panel 200 may include a second substrate 210, a lightblocking layer 220, an overcoat layer 230, a spacer 240, a secondelectrode (also called a common electrode) CE, a second dam 250, and asecond alignment layer 260.

The second substrate 210 may include a display region DA and anon-display region NDA that are defined on the second display panel 200.The second substrate 210 may be oppositely coupled to the firstsubstrate 110, and may have a size that is smaller than the size of thefirst substrate 110. Accordingly, the second substrate 210 may cover thedisplay region DA of the first substrate 110 and may expose a part ofthe non-display region NDA. In the same manner as the first substrate110, the second substrate 210 may include an insulating material, suchas transparent glass, quartz, ceramic, silicon, or transparent plastic,and may be appropriately selected in accordance with a need of amanufacturer. In some embodiments, the second substrate 210 may haveflexibility. The second substrate 210 may be a substrate having a shapethat is changeable, for example, by rolling, folding, or bending.

The light blocking layer 220 may be arranged on the second substrate210. For example, the light blocking layer 220 may be arranged on alower portion of the second substrate 210. The light blocking layer 220may be arranged in the non-display region NDA and in a non-pixel regionin which a thin film transistor TR is arranged, on the second substrate210. The light blocking layer 220 may overlap a gate line, a data line,and the thin film transistor TR. The light blocking layer 220 may beformed of a light blocking material to intercept undesired light inimplementing an image. For example, the light blocking layer 220 mayintercept light leakage that could occur at edges of the liquid crystallayer LCL or color mixing that could occur at edges of the color filter140. Although FIG. 2 illustrates that the light blocking layer 220 doesnot overlap the edges of the color filter 140, in some implementations,the light blocking layer 220 may overlap the edges of the color filter140.

The overcoat layer 230 may be arranged on the second substrate 210 tocover the light blocking layer 220. The overcoat layer 230 may serve toprotect and planarize the light blocking layer 220. The overcoat layer230 may be formed using an acrylic epoxy material.

The second electrode CE may be arranged on the overcoat layer 230 overthe entire surfaces of the display region DA and the non-display region.The second electrode CE may receive a common voltage from a common lineand may generate an electric field together with the first electrode PEto control the alignment direction of the liquid crystal molecules LCincluded in the liquid crystal layer LCL. The second electrode mayinclude a transparent conductive material. For example, the secondelectrode CE may include indium tin oxide (ITO) or indium zinc oxide(IZO).

The column spacer 240 may be arranged on the second electrode CE in aportion of the non-pixel region of the display region DA where the firstelectrode PE is not arranged. The column spacer 240 may maintain a cellgap between the first display panel 100 and the second display panel200. The column spacer 240 may include an organic material. Asillustrated in FIG. 2, the column spacer 240 may be positioned in aregion that corresponds to the thin film transistor.

The second dam 250 may be arranged on the second substrate 210 in aregion of the non-display region NDA that is adjacent to the displayregion DA. For example, the second dam 250 may be arranged on the secondelectrode CE so as to not overlap the first dam 160. In this case, whenthe first display panel 100 and the second display panel 200 are coupledto each other, interference between the first dam 160 and the second dam250 may be reduced in a determined cell gap between the first displaypanel 100 and the second display panel 200. The second dam 250 mayinclude a second barrier 251 and a second stopper 252 that are stackedin the third direction Z.

The second barrier 251 may be arranged on the same layer as the columnspacer 240, for example, between the second electrode CE and the liquidcrystal layer LCL. The second barrier 251 may extend to surround thedisplay region DA of the second substrate 210 and may form a closedcurve. The second barrier 251 may have a predetermined thickness T11 (inFIG. 3).

The second stopper 252 may be arranged on the second electrode CE tooverlap the second barrier 251. For example, like the second barrier251, the second stopper may also extend to surround the display regionDA of the second substrate 210 to form a closed curve. The secondstopper 252 may have a lyophobic characteristic with respect to analignment solution that is used when the second alignment layer 260 isformed. The second stopper 252 may have a thickness that is less thanthe thickness T11 (in FIG. 3) of the second barrier 251. For example,the maximum thickness T12 (in FIG. 3) of the second stopper 252 may beless than the thickness T11 (in FIG. 3) of the second barrier 251.

The second stopper 252 may be formed using a dispensing process. Thesecond stopper 252 may include an alignment material having thelyophobic characteristic with respect to the alignment solution that isused when the second alignment layer 260 is formed. The alignmentmaterial of the second stopper 252 may be an organic polymer material.The organic polymer material may include, for example, at least one of apolyimide, a polyamic acid, and a polysiloxane.

When the second alignment layer 260 is formed on the second electrode CEusing a printing method, such as an inkjet printing method, to apply analignment solution including an alignment material, the second dam 250may help to prevent the alignment solution that is discharged onto thesecond electrode CE from spreading toward the non-display region NDA dueto spread properties of the alignment solution. For example, the secondbarrier 251 having the predetermined thickness T11 may serve toprimarily prevent the above-described spreading, and the second stopper252 having the lyophobic characteristic with respect to the alignmentsolution may serve to secondarily prevent the spreading. The details ofthe second dam 250 will be described below.

The second alignment layer 260 may be arranged to cover the displayregion DA of the second substrate 210, and, for example, to cover thesecond electrode CE and the column spacer 240. At least a part of thesecond alignment layer 260 may extend up to the non-display region NDAof the second substrate 210 to come into contact with the surface of thesecond stopper 252 of the second dam 250. In this case, a portion 260Tof the second alignment layer 260 may overlap a portion of a concavegroove g2 (in FIG. 3) of the second stopper 252. Such a structure may beobtained in accordance with the limiting of flowing of the alignmentsolution to the non-display region NDA by the second stopper 252, whichhas the lyophobic characteristic with respect to the alignment solutionthat is discharged onto the second electrode CE and in accordance withincreasing a resistive force against the flowing of the alignmentsolution to the non-display region NDA using the groove g2 (in FIG. 3),in the case where the second alignment layer 260 is formed using aprinting method, such as an inkjet printing method. In someimplementations, in order to obtain good wettability of the alignmentsolution with respect to the second electrode CE when the secondalignment layer 260 is formed, the surface of the second substrate 210,on which the second electrode CE is formed, may have been treated suchthat the whole surface of the second substrate 210 has the lyophiliccharacteristic.

The second alignment layer 260 as described above may serve to initiallyalign liquid crystal molecules LC of the liquid crystal layer LCL. Thesecond alignment layer may include an alignment material. The alignmentmaterial of the second alignment layer 260 may be an organic polymermaterial. The organic polymer material may include, for example, atleast one of a polyimide, a polyamic acid, and a polysiloxane.

A sealing member 300 may be interposed between the edge region of thenon-display region NDA of the first display panel 100 and the edgeregion of the non-display region NDA of the second display panel 200having the above-described configuration. The sealing member 300 mayextend to surround the display region DA of the first display panel 100and the display region DA of the second display panel 200, and may forma closed curve.

As described above, the sealing member 300 may couple the first displaypanel 100 and the second display panel 200 to each other. The sealingmember 300 may adhere to the third insulating layer 150 and the secondelectrode CE. The sealing member 300 may include, for example, anadhesive such as a sealant, as an example.

The liquid crystal layer LCL may be interposed between the displayregion DA of the first display panel 100 and the display region DA ofthe second display panel 200, for example, between the first alignmentlayer 170 and the second alignment layer 260. The liquid crystal layerLCL may be include the liquid crystal molecules LC having positive ornegative dielectric anisotropy.

Hereinafter, the detailed configuration of the dams 160 and 250 and thearrangement relationship between the dams 160 and 250 and the alignmentlayers 170 and 260 will be described in more detail.

FIG. 3 illustrates an enlarged cross-sectional view of portion “A” ofFIG. 2, and FIG. 4 illustrates a top view showing an arrangementrelationship between a first dam and a first alignment layer of FIG. 2.FIG. 4 exemplifies only the first display panel 100 that includes thefirst alignment layer 170, and the first dam 160 and the first alignmentlayer 170 are exaggeratedly illustrated.

Referring to FIGS. 3 and 4, the first barrier 161 of the first dam 160may extend to surround the display region DA of the first substrate 110.The first barrier 161 may form a closed curve. The first barrier 161 mayhave a predetermined thickness T1, for example, a thickness of about 3μm or more. When forming the first alignment layer 170 on the firstelectrode PE using a printing method, such as an inkjet printing method,the thickness T1 of the first barrier 161 may be set to a thicknesssufficient to primarily prevent the alignment solution including analignment material that is discharged onto the first electrode PE fromspreading toward the non-display region NDA. For example, the alignmentsolution discharged onto the first electrode PE may have a tendency tospread due to spread properties of the alignment solution, and suchspreading may be blocked by the first dam 160. The first barrier 161 maybe formed together with the color filter 140 in a patterning process. Inthis case, it may be possible to form the first barrier 161 with thepredetermined thickness T1 through the patterning process. When thefirst barrier 161 is formed through the patterning process, the firstbarrier 161 may be formed as a continuous straight line along eachextension direction surrounding the display region, as illustrated inFIG. 4.

The first barrier 161 may be formed of the same material as the colorfilter 140 arranged on the first substrate 110. For example, the firstbarrier 161 may include the same material as a blue filter of the colorfilter 140, or may include the same material as a red filter or a greenfilter. If the light blocking layer or the column spacer is formed onthe first substrate 110, the first barrier 161 may be formed of the samematerial as the light blocking layer or the column spacer.

The first stopper 162 of the first dam 160 may extend to surround thedisplay region DA of the first substrate 110 and may form a closedcurve. The first stopper 162 may include a concave groove g1 that isformed on the surface along the extension direction. For example, thefirst stopper 162 may have a large thickness at edge portions thereof incomparison to the center portion thereof in a direction that isperpendicular to the extension direction. The first stopper 162 havingthe above-described shape may be formed by a coffee ring effect duringdrying of the alignment solution after the alignment solution, which mayinclude an alignment material and may have a first viscosity, forexample, a viscosity that exceeds about 70 cP, is spread on the firstbarrier 161 using a dispensing process and then is dried. In someimplementations, the first alignment layer 170 may be formed bydischarging the alignment solution, which includes an alignment materialand has second viscosity, for example, viscosity in the range of about 6cp to 70 cp, on the first electrode PE (in FIG. 2) using a printingprocess and then drying the discharged alignment solution.

The minimum thickness T3 of the first stopper 162 may be equal to orgreater than the thickness T4 of the first alignment layer 170 that isarranged on the first electrode PE in the display region DA. The firststopper 162 may be formed from an alignment solution having a higherviscosity than the alignment solution of the first alignment layer 170.When the first stopper 162 is formed through the dispensing process, thefirst stopper 162 may be uneven along the extension direction, asillustrated in FIG. 4.

When the first stopper 162 is formed through the dispensing process, thefirst stopper 162 may have a thickness that is less than the thicknessof the first barrier 161 that is formed using the patterning process.For example, the maximum thickness T2 of the first stopper 162 may beless than the thickness T1 of the first barrier 161.

The first stopper 162 having the above-described structure may have athin thickness. When the first alignment layer 170 is formed using theprinting method, such as the inkjet printing method, the groove g1 mayheighten the resistive force against the flowing of the alignmentsolution that is discharged on the first electrode PE (in FIG. 2) towardthe non-display region NDA.

Further, in order to heighten the control effect to prevent thealignment solution that is discharged on the first electrode PE (in FIG.2) from spreading toward the non-display region NDA, the first stopper162 may include an alignment material having a lyophobic characteristicwith respect to the alignment solution. The alignment material of thefirst stopper 162 may be different from the alignment material of thefirst alignment layer 170. In this case, the lyophobic characteristic ofthe first stopper 162 may become greater with respect to the alignmentsolution that is used when the first alignment layer 170 is formed. Forexample, the first stopper 162 may be formed to include a polyimide thatis a constituent material of the first stopper 162 or a material havingother components.

When the first stopper 162 has a lyophobic characteristic with respectto the alignment solution that is used to form the first alignment layer170, the alignment solution may have a convex shape at one portion ofthe first stopper 162, and a part 170T of the first alignment layer 170that overlaps or comes into contact with the surface of the firststopper 162 may be formed with a thickness that is greater than thethickness of a portion that overlaps the first electrode PE (in FIG. 2)in the display region DA (in FIG. 2) of the first substrate 110.

The first dam 160, which includes the first barrier 161 and the firststopper 162, may be in the form of a single line along the extensiondirection. In other implementations, the first dam 160 may also be inthe form of a multiline.

The second barrier 251 of the second dam 250 may extend to surround thedisplay region DA of the second substrate 210. The second barrier 251may form a closed curve. The second barrier 251 may have a predeterminedthickness T11, for example, a thickness of about 3 μm or more. Whenforming the second alignment layer 260 on the second electrode CE usinga printing method, such as an inkjet printing method, the thickness T11of the second barrier 251 may be set to a thickness sufficient toprimarily prevent the alignment solution including an alignment materialthat is discharged onto the second electrode CE from spreading towardthe non-display region NDA. For example, the alignment solutiondischarged onto the second electrode CE may have a tendency to spreaddue to spread properties of the alignment solution, and such spreadingmay be blocked by the second dam 250. The second barrier 251 may beformed together with the column spacer 240 in a patterning process. Inthis case, it may be possible to form the second barrier 251 with thepredetermined thickness T11 through the patterning process. When thesecond barrier 251 is formed through the patterning process, the secondbarrier may be formed as a continuous straight line along each extensiondirection surrounding the display region.

The second barrier 251 may include the same material as the columnspacer 240 that is arranged on the second substrate 210. When the lightblocking layer or the color filter is formed on the second substrate210, the second barrier 251 may be formed of the same material as thelight blocking layer or the color filter.

The second stopper 252 of the second dam 250 may extend to surround thedisplay region DA of the second substrate 210 on the second barrier 251.The second stopper 252 may form a closed curve. The second stopper 252may include a concave groove g2 that is formed on the surface thereofalong the extension direction. For example, the second stopper 252 mayhave a large thickness at edge portions thereof in comparison to thecenter portion thereof in a direction that is perpendicular to theextension direction. The second stopper 252 having the above-describedshape may be formed t by a coffee ring effect during drying of thealignment solution after the alignment solution, which may include analignment material and may have a first viscosity, for example, aviscosity that exceeds about 70 cP, is spread on the second barrier 251using a dispensing method and then is dried. In some implementations,the second alignment layer 260 may be formed by discharging thealignment solution, which includes an alignment material and has secondviscosity, for example, viscosity in the range of about 6 cp to 70 cp,on the second electrode CE (in FIG. 2) using a printing process and thendrying the discharged alignment solution.

The minimum thickness T13 of the second stopper 252 may be equal to orgreater than the thickness T14 of the second alignment layer 260 that isarranged on the second electrode CE in the display region DA. The secondstopper 252 may be formed from an alignment solution having a higherviscosity than the alignment solution of the second alignment layer 260.When the second stopper 252 is formed through the dispensing process,the first stopper 252 may be uneven along the extension direction likethe first stopper 162 as illustrated in FIG. 4.

When the second stopper 252 is formed through the dispensing process,the first stopper 252 may have a thickness that is less than thethickness of the second barrier 251 that is formed using the patterningprocess. For example, the maximum thickness T12 of the second stopper252 may be less than the thickness T11 of the second barrier 251.

The second stopper 252 having the above-described structure may have athin thickness. When the second alignment layer 260 is formed using theprinting method, such as the inkjet printing method, the groove g2 mayheighten the resistive force against the flowing of the alignmentsolution that is discharged on the second electrode CE (in FIG. 2)toward the non-display region NDA.

Further, in order to heighten the control effect to prevent thealignment solution that is discharged on the second electrode CE (inFIG. 2) from spreading toward the non-display region NDA, the secondstopper 252 may include an alignment material having a lyophobiccharacteristic with respect to the alignment solution. The alignmentmaterial of the second stopper 252 may be different from the alignmentmaterial of the second alignment layer 260. In this case, the lyophobiccharacteristic of the second stopper 252 may become greater with respectto the alignment solution that is used when the second alignment layer260 is formed. For example, the second stopper 252 may be formed toinclude a polyimide that is a constituent material of the second stopper252 or a material having other components.

When the second stopper 252 has a lyophobic characteristic with respectto the alignment solution that is used to form the second alignmentlayer 260, the alignment solution may have a convex shape at one portionof the second stopper 252, and a part 260T of the second alignment layer260 that overlaps or comes into contact with the surface of the secondstopper 252, may be formed with a thickness that is greater than thethickness of a portion that overlaps the second electrode CE (in FIG. 2)in the display region DA (in FIG. 2) of the second substrate 210.

The second dam 250, which includes the second barrier 251 and the secondstopper 252, may be arranged in the form of a single line shape alongthe extension direction or in the form of a multiline.

As described above, the display device 10 according to an embodiment maybe provided with the first dam 160 that includes the first barrier 161having the predetermined thickness T1 and the first stopper having thelyophobic characteristic with respect to the alignment solution that isused to form the first alignment layer 170. Accordingly, the thicknessof the dam may be minimized, and the spreading of the alignment solutionthat is used to form the first alignment layer 170 onto the non-displayregion NDA of the first substrate 110 may be reduced.

Accordingly, the increase of the width of the non-display region NDA inthe display device 10 can be reduced, and thus a slim bezel can beprovided.

FIGS. 5 to 7 are cross-sectional views showing various embodiments of afirst dam and a second dam.

FIG. 5 exemplifies that a first dam 160 a includes a first barrier 161and a first stopper 162 a having a width that is smaller than the widthof the first barrier 161. The width of the first stopper 162 a may becontrolled through adjustment of the amount of an alignment solutionthat is used to form the first stopper 162 a.

The first dam 160 a may heighten the resistive force against flowing ofthe alignment solution of the first alignment layer 170 a to thenon-display region NDA through forming of a step portion on a sideportion of the first barrier 161 and a side portion of the first stopper162 a. Accordingly, the flowing of the alignment solution of the firstalignment layer 170 a to the non-display region may be reduced moreeffectively.

A second dam 250 a may include a second barrier 251 and a second stopper252 a arranged on the second barrier 251 and having a width that issmaller than the width of the second barrier 251. The second dam 250 amay play the same role as the first dam 160 a with respect to the secondalignment layer 260 a.

FIG. 6 exemplifies that a first dam 160 b includes a first barrier 161and a first stopper 162 b that is arranged on at least a part of a sidesurface and an upper surface of the first barrier 161. The first stopper162 b may be formed when a large amount of alignment solution that isused to form the first stopper 162 b is spread on the upper surface ofthe first barrier 161 such that the alignment solution flows to the sidesurface of the first barrier 161. A portion that is formed on the uppersurface of the first stopper 162 b and a portion that is formed on theside surface of the first stopper 162 b may be formed as a continuousshape.

When the first dam 160 b has a wide region through the first stopper 162b and has the lyophobic characteristic with respect to the alignmentsolution of the first alignment layer 170 b, the control effect toprevent the alignment solution of the first alignment layer 170 b fromspreading toward the non-display region NDA may be heightened.Accordingly, the flowing of the alignment solution of the firstalignment layer 170 b to the non-display region NDA may be reduced moreeffectively.

The second dam 250 b may include a second barrier 251 and a secondstopper 252 b arranged on at least a part of a side surface and an uppersurface of the second barrier 251. A portion that is formed on the uppersurface of the second stopper 252 b and a portion that is formed on theside surface of the second stopper 252 b may be formed as a continuousshape. The second dam 250 b may play the same role as the first dam 160b with respect to the second alignment layer 260 b.

FIG. 7 exemplifies that a first dam 160 c may include a first barrier161 and a first stopper 162 c that is arranged on at least a part of aside surface and an upper surface of the first barrier 161. A portionthat is formed on the upper surface of the first stopper 162 c and aportion that is formed on the side surface of the first stopper 162 cmay be separated or spaced apart. In some implementations, the portionsof the first stopper 162 c may be formed on the third insulating layer150 before and after the first barrier 161 in a flowing direction of thealignment solution.

The first dam 160 c may have an accommodation groove formed thereon tohold therein the alignment solution of the first alignment layer 170 bwhen the alignment solution of the first alignment layer 170 b movestoward the non-display region NDA through the first stopper 162 c.Accordingly, the flowing of the alignment solution of the firstalignment layer 170 c to the non-display region NDA can be reduced moreeffectively.

The second dam 250 c may include a second barrier 251 and a secondstopper 252 c arranged on at least a part of a side surface and an uppersurface of the second barrier 251. A portion that is formed on the uppersurface of the second stopper 252 c and a portion that is formed on theside surface of the second stopper 252 c may be separated or spacedapart. In some implementations, the portions of the first stopper 162 cmay be formed on the third insulating layer 150 before and after thefirst barrier 161 in a flowing direction of the alignment solution 260c. The second dam 250 c may play the same role as the first dam 160 cwith respect to the second alignment layer 260 c.

Next, a method for fabricating a display device 10 according to anembodiment will be described.

FIGS. 8 to 18 illustrate cross-sectional views explaining stages of amethod for fabricating a display device of FIG. 1.

Referring to FIG. 8, a first substrate 110 that includes a displayregion DA and a non-display region NDA that is arranged on an outside ofthe display region DA to surround the display region DA may be prepared.On the first substrate 110, a thin film transistor TR, a firstinsulating layer 120, and a second insulating layer 130 may be formedalong a third direction Z. Such configuration is described above indetail with regard to FIG. 2.

Referring to FIGS. 9 to 11, a first dam 160, which includes a firstbarrier 161 and a first stopper 162 that are stacked in a region of thenon-display region NDA that is adjacent to the display region DA in athird direction Z, may be formed on the first substrate 110.

For example, referring to FIG. 9, the first barrier 161 may be formed onthe second insulating layer 130 in the region of the non-display regionNDA that is adjacent to the display region DA. The first barrier 161 mayextend to surround the display region DA on the second insulating layer130, and may form a closed curve. The first barrier 160 may be formed onthe second insulating layer 130 together with a color filter 140 by apatterning method when the color filter 140 is formed in the displayregion DA.

Referring to FIG. 10, a third insulating layer 150 may be formed in thedisplay region DA and the non-display region NDA on the secondinsulating layer 130 to cover the color filter 140 and the first barrier161.

Referring to FIG. 11, a first stopper 162 may be formed on the thirdinsulating layer 150 to overlap the first barrier 161. The first stopper162 may be formed by spreading an alignment solution, which includes analignment material and has a first viscosity, for example, a viscositythat exceeds about 70 cP, on the first barrier 161 using a dispensingprocess. A concave groove may be formed on the surface of the firststopper 162. The first stopper 161 may form a first dam 160 togetherwith the first barrier 161.

Referring to FIG. 12, a first alignment layer 170 may be formed in thedisplay region DA of the first substrate 110, and, for example, on afirst electrode PE and the third insulating layer 150. The firstalignment layer 170 may be formed by discharging an alignment solutionthat includes an alignment material that is different from the alignmentmaterial of the first stopper 162 and that has a second viscosity thatis lower than the first viscosity onto the first electrode PE and thethird insulating layer 150 using a printing method, such as an inkjetprinting method, and then drying the discharged alignment solution Theviscosity of the alignment solution used to form the first alignmentlayer 170 may be in the range of, for example, about 6 cp to 70 cp.

Referring to FIG. 13, a second substrate 210 that includes a displayregion DA and a non-display region NDA that are positioned on an outsideof the display region DA to surround the display region DA may beprepared. On the second substrate 210, a light blocking layer 220, anovercoat layer 230, and a second electrode CE, which are stacked in athird direction Z, may be formed. Such configuration described in detailabove with regard to FIG. 2.

Referring to FIGS. 14 and 15, a second dam 250, which includes a secondbarrier 251 and a second stopper 252 that are stacked on a region of thenon-display region NDA that is adjacent to the display region DA in thethird direction Z, may be formed on the second substrate 210.

For example, referring to FIG. 14, the second barrier 251 may be formedin the region of the non-display region NDA that is adjacent to thedisplay region DA on the second electrode CE. The second barrier 252 mayextend to surround the display region DA on the second electrode CE, andmay form a closed curve. The second barrier 250 may be formed in apatterning process at the same time that the column spacer 240 is formedin the display region DA on the second electrode CE.

Referring to FIG. 15, a second stopper 252 may be formed on the secondelectrode CE to overlap the second barrier 251. The second stopper 252may be formed by spreading an alignment solution that includes analignment material and that has a first viscosity, for example, aviscosity that exceeds about 70 cP, on the second barrier 251 using adispensing process. A concave groove may be formed on the surface of thesecond stopper 252. The second stopper 252 may form a second dam 250together with the second barrier 251.

Referring to FIG. 16, a second alignment layer 260 may be formed in thedisplay region DA of the second substrate 210, for example, on thesecond electrode CE and the column spacer 240. The second alignmentlayer 260 may be formed by discharging the alignment solution, whichincludes an alignment material that is different from the alignmentmaterial of the second stopper 252 and has a second viscosity that islower than the first viscosity onto the second electrode CE and thecolumn spacer 240 using a printing method, such as an inkjet printingmethod, and then drying the discharged alignment solution. For example,the viscosity of the alignment solution used to form the secondalignment layer may be in the range of about 6 cp to 70 cp.

Referring to FIG. 17, a liquid crystal layer LCL may be formed byproviding of liquid crystal molecules LC onto the first electrode PE. Inimplementations, the liquid crystal layer LCL may be formed by providingof the liquid crystal molecules LC onto the second electrode 210.

Referring to FIG. 18, a display device 10 may be formed by coupling afirst display panel 100 and a second display panel 200 in a state wherea sealing member 300 is interposed between the first display panel 100and the second display panel 200. The liquid crystal layer LCL may beinterposed between the first alignment layer 170 and the secondalignment layer 260.

By way of summation and review, In a typical liquid crystal display, twosubstrates, between which a liquid crystal layer is interposed, arebonded together by a sealing member. On each surface of the twosubstrates, an alignment layer for determining an initial alignmentdirection is arranged.

Generally, the alignment layer is formed by discharging an alignmentsolution that includes an alignment material (alignment solid content)on the surfaces of the two substrates using an inkjet printing methodand drying the discharged alignment solution. However, while thealignment solution is discharged using the inkjet printing method, thealignment solution may spread toward an outside of the two substrates,that is, toward a non-display region, due to spread properties of thealignment solution. In this case, a gap between the sealing member thatis arranged in the non-display region of the two substrates and adisplay region on which a pixel electrode is arranged may become large,which may cause a width of the non-display region of the liquid crystaldisplay also to become large. As a result, it may be difficult toimplement a slim bezel that covers the non-display region of the twosubstrates. Accordingly, a dam between the sealing member and thedisplay region in which the pixel electrode is arranged is desirable toreduce spreading of the alignment solution.

Generally, a dam may be formed through a patterning process at the sametime that a color filter, a column spacer, or a black matrix of theliquid crystal display is formed. The dam may be composed of a singlelayer having a predetermined thickness. However, although it isdesirable to increase the thickness of the dam in order to reduce thespreading of the alignment solution, there is a limit to how much thethickness of the dam may be increased within a predetermined cell gap ofthe liquid crystal display.

Embodiments provide a display device that can provide a slim bezelthrough minimization of a thickness of a dam and reduction of spreadingof an alignment solution.

Embodiments further provide a method for fabricating a display devicethat can provide a slim bezel through minimization of a thickness of adam and reduction of spreading of an alignment solution.

Example embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation.Accordingly, it will be understood by those of skill in the art thatvarious changes in form and details may be made without departing fromthe spirit and scope thereof as set forth in the following claims.

What is claimed is:
 1. A display device, comprising: a substrateincluding a display region and a non-display region, the non-displayregion being positioned on an outside of the display region; a secondlayer disposed in the non-display region of the substrate; a third layerbetween the substrate and the second layer, and a fourth layer coveringthe display region of the substrate, at least a part of the fourth layerextending to the non-display region and contacting a surface of thesecond layer, wherein the second layer covers side surfaces of the thirdlayer and an upper surface of the third layer, a thickness of the secondlayer is less than a thickness of the third layer, and a thickness ofthe second layer disposed on the upper surface of the third layer isgreater than a thickness of the second layer disposed on the sidesurfaces of the third layer.
 2. The display device as claimed in claim1, wherein the second layer disposed on the upper surface of the thirdlayer has an indentation pattern indented toward the upper surface ofthe third layer.
 3. The display device as claimed in claim 2, wherein: aminimum thickness of the second layer is equal to or greater than aminimum thickness of a portion of the fourth layer that is in thedisplay region of the substrate, and a portion of the fourth layer thatcontacts the surface of the second layer has a maximum thickness that isgreater than a maximum thickness of a portion of the layer that is inthe display region of the substrate.
 4. The display device as claimed inclaim 1, further comprising a color filter in the display region of thesubstrate.
 5. The display device as claimed in claim 4, wherein: thethird layer includes a same material as the color filter, each of thesecond layer and the fourth layer includes an organic polymer, and theorganic polymer of the second layer is different from the organicpolymer of the fourth layer.
 6. The display device as claimed in claim5, wherein the second layer has a lyophobic characteristic with respectto the fourth layer.
 7. The display device as claimed in claim 1,wherein at least a part of the fourth layer is disposed on an uppersurface of the surface of the second layer.
 8. The display device asclaimed in claim 1, further comprising a liquid crystal layer directlyon the second layer in the display region.
 9. A display device,comprising: a substrate including a display region and a non-displayregion, the non-display region being positioned on an outside of thedisplay region; a second layer disposed in the non-display region of thesubstrate; a third layer between the substrate and the second layer, anda fourth layer covering the display region of the substrate, at least apart of the fourth layer extending to the non-display region andcontacting a surface of the second layer, wherein the second layercovers side surfaces of the third layer and an upper surface of thethird layer with the second layer disposed on the upper surface of thethird layer having an indentation pattern indented toward the uppersurface of the third layer, and a maximum thickness of the second layeris less than a thickness of the third layer.
 10. The display device asclaimed in claim 9, wherein the maximum thickness of the second layerdisposed on the upper surface of the third layer is greater than themaximum thickness of the second layer disposed on the side surfaces ofthe third layer.
 11. The display device as claimed in claim 9, wherein:a minimum thickness of the second layer is equal to or greater than athickness of a portion of the fourth layer that is in the display regionof the substrate, and a portion of the fourth layer that contacts thesurface of the second layer has a thickness that is greater than athickness of a portion of the layer that is in the display region of thesubstrate.
 12. The display device as claimed in claim 9, wherein atleast a part of the fourth layer is disposed on an upper surface of thesurface of the second layer.
 13. A display device, comprising: asubstrate including a display region and a non-display region, thenon-display region being positioned on an outside of the display region;a color filter in the display region of the substrate; a second layerdisposed in the non-display region of the substrate; a third layerbetween the substrate and the second layer, the third layer including asame material as the color filter; and a fourth layer covering thedisplay region of the substrate, at least a part of the fourth layerextending to the non-display region and contacting a surface of thesecond layer, wherein the second layer covers side surfaces of the thirdlayer and an upper surface of the third layer, and a maximum thicknessof the second layer is less than a thickness of the third layer.
 14. Thedisplay device as claimed in claim 13, wherein: each of the second layerand the fourth layer includes an organic polymer, and the organicpolymer of the second layer is different from the organic polymer of thefourth layer.
 15. The display device as claimed in claim 13, wherein thesecond layer has a lyophobic characteristic with respect to the fourthlayer.
 16. The display device as claimed in claim 13, wherein at least apart of the fourth layer is disposed on an upper surface of the surfaceof the second layer.